The invention presented herein relates to switching circuitry that is connectable between an electrically powered circuit and a remote control signal circuit for supplying d.c. power to the remote control signal circuit from the electrically powered circuit and is connectable with the remote control signal circuit for receiving binary logic control signals from the remote control signal circuit. Such switching circuitry is operative in response to a logic control signal from the remote control circuit to provide a low impedance path across the connection made by the switching circuitry to the electrically powered circuit. In particular, the invention relates to an improvement to such switching circuitry involving the use of metal-oxide-semiconductor field-effect transistors in the switching circuitry allowing the switching circuitry to have broader application.
Situations arise wherein an electrically powered circuit is operable in response to the application of a momentary low impedance path such as may be provided by momentary closure of a switch. In cases where it is desirable to provide for operation of such an electrically powered circuit by an add-on circuit that is to be connected by a consumer-user, it is desirable that it be applicable to as many of the particular electrically powered circuits of various manufacture as possible and that it be connectable without concern for electrical polarity of whether d.c. or a.c. is involved.
One example of the situation just described involves the electrically powered circuit used for automatic garage door openers. Such circuitry is operable to open and close a garage door in response to the momentary closure of a switch by the user. It was recognized that it would be desirable to have an add-on circuit remote control signal including a keyboard switch panel mounted outside the garage entrance, which, upon entry of a code by manual operation, would cause circuitry that is located within the garage entrance and connected between the keyboard switch panel and automatic garage door opener circuitry to provide for momentary operation of a switch means included in switching circuitry to effect operation of the garage door opener circuitry. Such circuitry is disclosed in United States patent application Ser. No. 316,233, filed by Daryl D. Dressler on Oct. 29, 1981. The switching circuitry disclosed in the above-mentioned patent application includes a conventional full-wave rectifier formed by the interconnection of four diodes. The input of the full-wave rectifier is connectable to an electrically powered circuit and has its output connected to a control signal circuit via a power storage circuit portion of the switching circuit. The control signal circuit has an output which provides logic 1 or logic 0 signals. A switch means provided by the switching circuit is connected across the output of the full-wave rectifier. A transistor provides the switch means. The base of the transistor is arranged to receive a logic 1 or logic 0 signal from the control signal circuit.
While the switching circuit described provides an impedance path that is sufficiently low so that it is effective for use with the circuitry for a large number of different automatic garage door opener circuits to cause the garage door opener circuitry to operate, it presents an impedance path that is too high to allow the switching circuit to be used with garage door opener circuits that use a microprocessor.